Well Courtesy lists it here as part 40700M in this diagram:
253 Electrical Unit :: Body Electrical :: Genuine Nissan Parts :: 370Z Parts (Z34) 2009+ :: CourtesyParts.com
But there's no link for price/purchasing. I imagine anyone can source this though. If they're cheap I might go this route too, it would allow me to just take my new tires and wheels down for mounting and balancing without taking my old set off and unmounting the tires just to get the sensors out.